Cystic fibrosis (CF) is a generalized exocrinopathy in which the basic defect is still unknown. Studies have been pursued to determine the characteristics of the disease which are primary and related to a gene defect rather than secondary manifestations. The abnormal fatty acid pattern in patients with CF has been found to be a secondary effect of pancreatic insufficiency. Dysfunction of the endocrine system within the pancreas is also only seen in those patients with pancreatic insufficiency. New diagnostic methods for evaluating the degree of pancreatic involvement have been investigated. The use of a specific substrate for chymotrypsin which can be given orally and which yields a metabolite which is excreted in the urine has been found to be reliable. Ultrasonography also appears to have a predictive value of the degree of fibrosis present in the pancreas. Echocardiography has been employed to demonstrate secondary cardiac involvement to be present even in patients with clinically mild disease.